socks5udp_sendto Subroutine

Purpose

Send UDP packets through a SOCKSv5 server.

Library

Standard C Library (libc.a)

Syntax

#include <stdlib.h>
#include <netinet/in.h>
#include <sys/socket.h>

int socks5udp_sendto (Socket, Message, MsgLen, Flags, Dst, DstLen, Svr, SvrLen)
int Socket;
void *Message;
size_t MsgLen;
int Flags;
struct sockaddr *Dst;
size_t DstLen;
struct sockaddr *Svr;
size_t SrvLen;

Description

The socks5udp_sendto subroutine sends a UDP packet to Svr for relay to Dst. Svr must be the rendezvous address returned from a previous call to socks5udp_associate.

Socket must be an open socket descriptor of type SOCK_DGRAM; Dst and Svr may be either IPv4 or IPv6 addresses.

The socket applications can be compiled with COMPAT_43 defined. This will make the sockaddr structure BSD 4.3 compatible. For more details refer to socket.h.

Parameters

Item	Description
Socket	Specifies the unique name of the socket.
Message	Specifies the address containing the message to be sent.
MsgLen	Specifies the size of the message in bytes.
Flags	Allows the sender to control the message transmission. See the description in the sendto subroutine for more specific details.
Dst	Specifies the external address to which the SOCKSv5 server will attempt to relay the UDP packet.
DstLength	Specifies the length of the address structure in Dst.
Svr	Specifies the address of the SOCKSv5 server to send the UDP packet for relay.
SvrLength	Specifies the length of the address structure in Svr.

Return Values

Upon successful completion, the socks5udp_sendto subroutine returns a value of 0.

If the socks5udp_sendto subroutine is unsuccessful, the system handler performs the following functions:

Returns a value of -1 to the calling program.
Moves an error code, indicating the generic system error, into the errno global variable.
Moves an error code, indicating the specific SOCKSv5 error, into the socks5_errno global variable.

Error Codes (placed in errno; inherited from underlying call to sendto())

The socks5tcp_connect subroutine is unsuccessful if any of the following errors occurs:

Error	Description
EBADF	The Socket parameter is not valid.
ENOTSOCK	The Socket parameter refers to a file, not a socket.
EAFNOSUPPORT	The addresses in the specified address family cannot be used with this socket.
ENETUNREACH	No route to the network or host is present.
EINVAL	One or more of the specified arguments is invalid.
ENETDOWN	The specified physical network is down.
ENOSPC	There is no space left on a device or system table.

Error Codes (placed in socks5_errno; SOCKSv5-specific errors)

The socks5tcp_connect subroutine is unsuccessful if any of the following errors occurs:

Error	Description
S5_ESRVFAIL	General SOCKSv5 server failure.
S5_EPERM	SOCKSv5 server ruleset rejection.
S5_ENETUNREACH	SOCKSv5 server could not reach target network.
S5_EHOSTUNREACH	SOCKSv5 server could not reach target host.
S5_ECONNREFUSED	SOCKSv5 server connection request refused by target host.
S5_ETIMEDOUT	SOCKSv5 server connection failure due to TTL expiry.
S5_EOPNOTSUPP	Command not supported by SOCKSv5 server.
S5_EAFNOSUPPORT	Address family not supported by SOCKSv5 server.
S5_ENOSERV	No server found.

Examples

The following program fragment illustrates the use of the socks5udp_sendto subroutine by a client to request a connection from a server's socket.

void *message;
size_t msglen;
int flags;
struct sockaddr_in svr;
struct sockaddr_in6 dst;
.
.
.
socks5udp_associate(s,(struct sockaddr*)&dst, sizeof(dst), (struct sockaddr *)&svr, sizeof(svr));
.
.
.
socks5udp_sendto(s, message, msglen, flags (struct sockaddr*)&dst, sizeof(dst), (struct sockaddr *)&svr, sizeof(svr));